Thread trimming device for sewing machines

ABSTRACT

A manually operated thread cutting attachment for a sewing machine which may be used in place of the conventional sewing machine presser foot. A manually operable drive wheel is fastened on a short shaft journaled in an enlarged presser foot shank and extending in the direction of feed. Secured to the front of the shaft is a disk-like member carrying on its periphery a thread engaging finger, which when the shaft is initially manually turned, swings across the top of the presser foot sole plate and engages the needle thread, drawing it slightly to one side of the needle hole in the presser foot sole plate. The thread engaging finger remains in this position by means of a latch member mounted with the knurled drive wheel while the operator turns the hand wheel of the machine. As the needle descends to form the next stitch, it lays a needle thread loop over the threading engaging finger. The knurled drive wheel is thereafter further manually rotated causing the thread engaging finger to pull upwardly and outwardly on the needle thread and thereby draw bobbin thread up through the throat plate so that both the needle thread and the bobbin thread extend up through the hole in the presser foot sole plate in position to be cut by a knife slidably mounted in the presser foot. The knife is actuated by a further turning of the knurled drive wheel which causes a strike on the disk-like member to engage and slide the knife. When thread severing is completed a spring effects return of the thread engaging finger to its initial position.

United States Patet 1 1 Fox 1 Dec. 18, 1973 1 THREAD TRIMMING DEVICE FOR SEWING MACHINES [75] Inventor: Douglas J. Fox, Halton, England [73] Assignee: The Singer Company, New York,

[22] Filed: Dec. 21, 1972 [21] Appl. No.: 317,501

[52] US. Cl. 112/252, 112/262 [51] Int. Cl D05b 65/00 [58] Field of Search 112/65, 122, 130, 112/252, 253, 262

[56] References Cited UNITED STATES PATENTS 1,846,628 2/1932 Castagna [12/252 2,372,318 3/1945 Enos 112/252 2,508,236 5/1950 Enos 1. 112/252 3,124,089 3/1964 Diehm et a1. 112/252 3,584,589 6/1971 Pirrello 112/252 FOREIGN PATENTS OR APPLICATIONS 1,004,028 3/1957 Germany 112/252 Primary ExaminerWerner H. Schroeder Attorney-Marshall J. Breen et al.

[57] ABSTRACT A manually operated thread cutting attachment for a sewing machine which may be used in place of the conventional sewing machine presser foot. A manually operable drive wheel is fastened on a short shaft journaled in an enlarged presser foot shank and extending in the direction of feed. Secured to the front of the shaft is a disk-like member carrying on its periphery a thread engaging finger, which when the shaft is initially manually turned, swings across the top of the presser foot sole plate and engages the needle thread, drawing it slightly to one side of the needle hole in the presser foot sole plate, The thread engaging finger remains in this position by means of a latch member mounted with the knurled drive wheel while the operator turns the hand wheel of the machine. As the needle descends to form the next stitch, it lays a needle thread loop over the threading engaging finger. The knurled drive wheel is thereafter further manually rotated causing the thread engaging finger to pull upwardly and outwardly on the needle thread and thereby draw bobbin thread up through the throat plate so that both the needle thread and the bobbin thread extend up through the hole in the presser foot sole plate in position to be cut by a knife slidably mounted in the presser foot. The knife is actuated by a further turning of the knurled drive wheel which causes a strike on the disk-like member to engage and slide the knife. When thread severing is completed a spring effects return of the thread engaging finger to its initial position.

13 Claims, 13 Drawing Figures PAIENTEHUEC18 1915 3,779,189

sum 1 or 2 PAIFNIEUUEC 1 8 192a 3.779.189

sum 2 or 2 Fig. 9

THREAD TRIMMING DEVICE FOR SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to a thread trimming device for sewing machines and more particularly to a presser foot attachment including thread pull off and severing mechanism for severing both the upper and lower threads of a two thread sewing machine.

It is a primary object of this invention to provide an inexpensive and simple thread cutting attachment for a two thread sewing machine which will draw the needle thread and bobbin thread up prone and sever the same. The known prior art devices and methods for drawing a length of needle thread and bobbin thread and for severing the same are expensive and sophisticated devices whose cost is only warranted in industrial sewing machines or other machines which are sold in high volume. Furthermore, prior art trimming attachments that have been developed in the past are not generally of the type which simultaneously sever the needle and bobbin threads. As exemplary of this latter type is the one shown in [1.5. Pat. No. 2,846,967 which is operable to sever the needle thread only. Moreover, the known prior art severing attachments require some modifications to the sewing machine.

The present invention provides a method for simultaneously severing the needle thread and bobbin thread and provides a novel device which may be installed in a sewing machine without any modification thereof to aid in performing the method.

It is therefore a further object of this invention to provide a thread severing device which may be readily mounted on a sewing machine in place of a conventional presser foot.

A still further object of this invention is to provide a novel method of severing both the needle and bobbin thread of a two thread sewing machine at the termination of a sewing sequence.

These objects and others are attained by a presser foot having a knife slidable over the needle accommodating hole, and which is activated by a striker supported on a member rotatable in a plane substantially normal to they sliding direction. The rotatable member is mounted on one end of a shaft journaled in an enlarged shank of the presser foot. A manually rotatable drive wheel is secured to the other end of the shaftbehind the presser foot shank. The rotatable striker support member includes a thread engaging finger which is adapted to draw a needle thread to one side of the needle accommodating hole when the drive wheel is initially turned. A latch mounted within the drive wheel operates in conjunction with a catch in a stop plate mounted on the presser foot shank and with a differential movement member to hold the finger in this position and subsequently to release the same as the drive wheel is turned. Proper coordination of the drive wheel and the sewing machine handwheel allows the finger to draw out, along with the needle thread, a length of bobbin thread through the needle accommodating hole and to hold the thread prone for severing.

BRIEF DESCRIPTION OF THE DRAWINGS The particular features and advantages of the invention, as well as other objects, will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a thread severing presser foot device constructed in accordance with the present invention;

FIG. 2 is a cross sectional view taken substantially midway through the shank and from front to rear (in the direction of feed) of the device of FIG. 1;

FIG. 3 is a disassembled perspective view of the device of FIG. 1 with a portion of the drive wheel cut away for clarity;

FIG. 4 is a cross sectional view taken along line 4-4 of FIG. 2 showing the internal structure of the drive wheel, and the components therein in their initial position;

FIG. 5 is a cross sectional view similar to FIG. 4 showing the elements in another position;

FIG. 6 is a cross sectional view similar to FIG. 4 showing the elements in still another position;

FIG. 7 is a view of the drive wheel viewed from the inside thereof; and

FIGS. 8-13 are elevational views partially in cross section illustrating the steps of the novel method of thread severing of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now the the accompanying drawings wherein like reference numerals denote similar parts throughout the several views, there is disclosed an attachment generally shown as 10 which includes an enlarged shank 12 adapted to be secured conventionally to a sewing machine presser bar 14 by a presser bar securing screw 16, only the head 18 being illustrated in the drawings (see FIG. 13). As is known in the sewing art a needle bar 20 having a needle 22 secured in the bottom end thereof is mounted for vertical reciprocation in the head. An upper or needle thread 24 is threaded through the eye 26 of the needle and cooperates with a lower or bobbin thread 28 to form stitches in the usual manner. It should be understood that the direction of sewing feed is into and substantially normal to the plane of the paper as viewed in FIGS. 8-13.

The shank 12 is pivotably secured between spaced upstanding walls 30 and 32 of a sole plate 34 by means of a threaded stud 36 which passes through a bore 38 in wall 30, and a bore 40 in the shank 12, and is threadedly received in a tapped bore 42 in the wall 32. The sole plate includes an oblong slot 44 through which the needle is adapted to pass. On the upper surface of the sole plate abutting the walls 30 and 32 is a pair of spaced bosses 46 and 48, while a third, but elongated boss 50 extends the width of the sole plate on the other side of the slot 44 and contains a portion of the slot. Positioned within the channel formed by the ends of the bosses 46 and 48 and the inner end of the boss 50 is a trimmer blade 52. The blade includes an open ended slot 54 which normally is positioned superposed above slot 44. One edge 56 of slot 54 is sharply grounded to form a knife edge. A cover plate 58 having an elongated slot 60 of substantially the same size and shape as the slot 44 is positioned on and secured to the tapped bosses by four screws 62, with the slot 60 superposed over the slot 44. The plate 58 is cutout at 64 to receive an upstanding lug 66 formed at one longitudinal edge of the blade 52 and which acts as a stop. At the other end of the blade 52 there is formed a larger upstanding lug or anbil 68. Secured to one of the screws 62 is a wire leaf spring 70 which abuts the inner surface of the anvil to bias the same to normally maintain the lug 66 against the inner edge of the cutout 64 so that the slot 60 is properly superposed over slot 44 to allow the needle to freely pass therethrough.

Formed in the shank 12 substantially parallel to the longitudinal axis of the sole plate 34 i.e., the direction of sewing feed is a bore 72 within which is press fitted a shouldered bushing 74 having a head 76 abutting the outer wall of the shank. Journaled within the bushing is a shaft 78, on one end of which is secured a disk-like member 80 having a bent thread drawing finger 82 mounted on the lower portion thereof. An elongated striker member 84 extends from the upper periphery of the member 80 at a location spaced substantially diametrically opposite to the finger. The member 80 includes an annular recess 86 and a protruding central hub 88 on the surface facing the shank. Also extending from that face radially spaced from the hub 88 is a pin 90 while a similar protuberance 92 extends from the face of the shank 12 above the bushing head 76. A coil spring 94 is mounted above the hub 88 and the head 76, which abut in the assembled position, and has one end secured in a hold 96 in the shank 12 and its other end secured in one of the holes 98 in the member 80. The spring 94 acts to bias the member 80 counterclockwise as shown in FIGS. 8 through 13, while the members 90 and 92 act as stops to limit the movement thereof.

Mounted on the wall of the shank remote from the member 80 by conventional means such as screws 1110 is a stop plate 102. This plate includes an annular hub 104 having a central bore 106 through which passes the free end of shaft 78. The hub 104 includes on the periphery thereof a segmental notch 108 extending on the circumference and recessed contiguous to the wall of the bore 106 from a point on the circumference directly above the center of the bore. Concentric with the hub 104 is a segmental annular ridge 1111 the ends of which define a pair of limit stops 112 and 114.

A disk-like differential movement plate member 116 having a peripherial flange 118 extending rearwardly from the face thereof and a central aperture 120 of substantially the same diameter as the hub 1114 is positioned about the hub. The flange is discontinuous to provide an opening defined between the edges 122 and 124. A pin 126 is formed on the stop plate facing surface of the member 116, and a pin 128 is formed on the opposite surface, but angularly displaced from the pin 126. The pin 128 is of substantially the same axial length as the axial thickness of the ridge 110 and radially is positioned so as to bebetween the stops 112 and 1 14.

A knurled drive wheel or drum 130, which includes a central bore 132 adapted to receive the free end of the shaft 78 and be secured thereto by conventional means such as screw 134, is formed on its inner face with a radially disposed arcuate slot 136. The pin 128 is longer than the axial length of the flange 118 and is adapted to be received within the slot 136. The depth of slot 136 is substantially equal to the difference between the length of the pin 128 and the flange 118 so that the flange abuts the surface 138 of the wheel 130 while the pin 128 is located adjacent the bottom surface of the slot 136. Also formed on the inner face of the wheel 130 is a non-radial substantially straight slot 140 and a hole 142.

Mounted between member 116 and wheel 130 is a latch 144 having a first pin 146 and a second pin 148,

extending from the rear surface thereof. The pin 146 is substantially midway between the ends of the member 144, while the pin 148 is adjacent one end thereof. The pin 148 extends into the slot and is urged to one end of the slot by a spring 150 positioned in the slot, 140 while the .pin 146 is positioned in the hole 142 when the wheel 130 is secured to the shaft 78. The latch member 144 is substantially arcuately shaped having a hook portion 152 at the end remote from the pin 148 and a protuberance 154 on its outer surface adjacent the pin 148.

In the initial position of operation, as shown in FIGS. 4 and 8, the protuberance 154 protrudes into the slot between edges 122 and 124 of the member 116. In this position of the attachment the operator turns the sewing machine handwheel until the point of the needle 22 has cleared the finger 82 on its upward movement. The operator then turns the knurled drive wheel 130 clockwise, as seen in FIG. 9, which in turn swings the finger 82 across the top of the sole plate so that it engages the needle thread drawing it slightly to the left side of the needle accommodating hole 44 in the sole plate. The protuberance 154 then rest against the inner wall of the knurl drive wheel 130 and engages the edge 122 of the flange 118 with the hook 152 of the latch member 144 enters the notch 108 to prevent the wheel 130, and thereby the finger 82, from returning to its initial position. The thread engaging finger 82 thereby remains in this intermediate position while the operator turns the handwheel of the machine, causing the needle to descend, as shown in FIG. 10, through the throat plate of the sewing machine to form the next stitch. This descent of the needle lays a needle thread loop over the thread engaging finger. After the second stitch is completed, as shown in FIG. 11, the knurled drive wheel 130 is further manually rotated clockwise, as shown in FIG. 12, causing the threading engaging finger 82 to draw up through the throat plate the bobbin thread so that both needle thread and bobbing thread extend up through the hole in the presser foot sole plate. As the wheel is rotated to the position shown in FIG. 12 the protuberance 154 pushing on the edge 122 of flange 118 turns the member 116 until the pin 126 is restrained by the stop 114, and as rotation continues the protuberance rides inside the flange 118 to pivotally lift the hook portion of the latch member 144 out of the recess as shown in FIG. 6. The bobbin thread and needle thread are now in a prone position to be cut by the knife 56 which is actuated by turning of the drive wheel 1311 until the striker member 84 engages the anvil 68 and drives it toward the left, as shown in FIG. 13, against the bias of the spring 70. Clockwise movement of the wheel 130 ends as the pin 128 reaches the end of the slot 136. At this stage the protuberance 154 of the latch member 144 has a clamping effect against the flange 118 and the inner wall of the wheel 1311. When the thread severing is completed the operator removes his hand from the drive wheel 130 which, by the operation of the spring 94, causes the wheel, the shaft 78 and finger 82 and the other elements of the device to rotate counterclockwise and return to their original position. Both the wheel 1311 and the member 1116 move as a unit until the pin 126 reaches the stop 112 on the plate 102. This ends rotation of the member 116 and, as the drive wheel 130 continues to rotate, the protuberance 154 of the latch 144 leaves the edge 122 of the flange 118 and is sprung into the gap between edge 122 and 124 by the spring 150. The device is then in its original position and ready for the next cycle.

It is thus seen that a simple and inexpensive device for accomplishing the object of the present invention is disclosed in this application. Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for purposes of illustration and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A thread trimming attachment for a sewing machine having a presser bar and sewing instnimentalities including a needle mounted for linear reciprocation carrying a needle thread cooperating with a bobbin thread to form stitches, said attachment comprising a presser foot including a shank and a sole plate said sole plate having a needle accommodating hole, means for securing said shank to said presser bar, a knife slidably mounted on said sole plate and normally biased to one side of said hole, a support member journaled in said shank, said member including a thread drawing finger and a striker member, means for biasing said support member normally to position said finger on said one side of said hole, and means for selectively turning said support member to move said finger from said one side to the other side of said hole thereby to draw a concatenation of needle thread and bobbin thread through said hole and to smite said striker against said knife to drive said knife across said hole to out both said needle and bobbin threads.

2. An attachment as recited in claim 1 wherein said support member includes a shaft journaled in said shank, said support member turning means comprising a manually operable drive wheelfast on said shaft.

3. An attachment as recited in claim 2 wherein said support member turning means includes latch means mounted within said wheel for locking said finger from returning to said one side of said hole upon initial positioning of said finger to the other said thereof and for allowing said finger to return to said one side upon en gagement of said striker with said knife.

4. An attachment as recited in claim 3 wherein said latch means comprises a latch member pivotably mounted in said wheel, a catch fixedly mounted on said shank and adopted to receive said latch member when the wheel is rotated to position said finger on said other side of the hole, and a member for lifting said latch member out of said catch when the wheel is rotated to substantially position the striker contiguous to said blade.

5. An attachment as recited in claim 1 wherein said knife includes a slot normally superposed over said needle accommodating hole, an anvil formed on said knife on the end adjacent said one sixe of said hole, a stop member formed on the other end of said knife, a plate member having a needle accommodating hole superposed over said knife secured to said sole, a spring secured to said plate member having one end abutting said anvil for biasing said knife toward said one side,

said stop member abutting said plate member when said knife slot is superposed over said needle accommodating hole.

6. An attachment as recited in claim 5 wherein said support member comprises a rotor mounted for rotation in a plane transverse to the direction of sewing feed, said thread drawing finger secured to said rotor and extending from a face thereof, said striker member secured to said roter and extending peripherally therefrom, a shaft secured to said rotor and extending from the face opposite to the finger extending face, and means journaling said shaft in said shank.

7. An attachment as recited in claim 6 wherein said support member turning means comprises a manually rotatable drum fast on said shaft adjacent said shank remote from said rotor, a stop plate including a shaft receiving central hub secured to said shank, means defining a catch in said hub, a latch member pivotably mounted in said drum and adapted to lock in said catch when said drum other rotated to initially position said finer on said othe side of the needle accommodating hole, and means for disengaging said latch from said catch upon further rotation of said drum.

8. An attachment as recited in claim 7 wherein said last named means comprises a disk member including a flange positioned within said drum about said hub, first and second stop means radially apaced on said stop plate, abuttment means on said disk member facing said stop plate in the same radial plane as said stop means, means defining an opening in said flange, a protuberance on said latch for abutting one edge of said flange opening to rotate said disk member until said disk member abuttment means engages a first of said stop means, said stop means and abuttment means being angularly positioned such that rotation of the drum may continue subsequent to stoppage of the disk.

9. The method of severing both the needle thread and the bobbin thread in a two thread sewing machine having a needle, and a presser foot including a needle accommodating hole, comprising the steps of:

a. drawing the needle thread to a first side of said hole.

b. holding said thread in this position while forming a stitch.

c. pulling the needle thread further away from said hole until a predetermined amount of bobbin thread is drawn therethrough, and

d. cutting both threads.

10. The method recited in claim 9 wherein the step of drawing the needle thread comprises the step of wip ing a thread engaging finger across the presser foot transverse to the direction of sewing feed to hook the thread.

11. The method recited in claim 10 wherein said finger holds said needle thread while the needle lays a needle thread loop over said finger.

12. The method of claim 1 1 wherein said step of pulling comprises lifting said finger with said thread loop thereon about a fixed axis away from said hole.

13. The method of claim 12 wherein said step of wiping and lifting said finger comprises rotating a finger mounted wheel. 

1. A thread trimming attachment for a sewing machine having a presser bar and sewing instrumentalities including a needle mounted for linear reciprocation carrying a needle thread cooperating with a bobbin thread to form stitches, said attachment comprising a presser foot including a shank and a sole plate said sole plate having a needle accommodating hole, means for securing said shank to said presser bar, a knife slidably mounted on said sole plate and normally biased to one side of said hole, a support member journaled in said shank, said member including a thread drawing finger and a striker member, means for biasing said support member normally to position said finger on said one side of said hole, and means for selectively turning said support member to move said finger from said one side to the other side of said hole thereby to draw a concatenation of needle thread and bobbin thread through said hole and to smite said striker against said knife to drive said knife across said hole to cut both said needle and bobbin threads.
 2. An attachment as recited in claim 1 wherein said support member includes a shaft journaled in said shank, said support member turning means comprising a manually operable drive wheel fast on said shaft.
 3. An attachment as recited in claim 2 wherein said support member turning means includes latch means mounted within said wheel for locking said finger from returning to said one side of said hole upon initial positioning of said finger to the other said thereof and for allowing said finger to return to said one side upon engagement of said striker with said knife.
 4. An attachment as recited in claim 3 wherein said latch means comprises a latch member pivotably mounted in said wheel, a catch fixedly mounted on said shank and adopted to receive said latch member when the wheel is rotated to position said finger on said other side of the hole, and a member for lifting said latch member out of said catch when the wheel is rotated to substantially position the striker contiguous to said blade.
 5. An attachment as recited in claim 1 wherein said knife includes a slot normally superposed over said needle accommodating hole, an anvil formed on said knife on the end adjacent said one sixe of said hole, a stop member formed on the other end of said knife, a plate member having a needle accommodating hole superposed over said knife secured to said sole, a spring secured to said plate member having one end abutting said anvil for biasing said knife toward said one side, said stop member abutting said plate member when said knife slot is superposed over said needle accommodating hole.
 6. An attachment as recited in claim 5 wherein said support member comprises a rotor mounted for rotation in a plane transverse to the direction of sewing feed, said thread drawing finger secured to said rotor and extending from a face thereof, said striker member secured to said roter and extending peripherally therefrom, a shaft secured to said rotor and extending from the face opposite to the finger extending face, and means journaling said shaft in said shank.
 7. An attachment as recited in claim 6 wherein said support member turning means comprises a manually rotatable drum fast on said shaft adjacent said shank remote from said rotor, a stop plate including a shaft receiving central hub secured to said shank, means defining a catch in said hub, a latch meMber pivotably mounted in said drum and adapted to lock in said catch when said drum other rotated to initially position said finer on said other side of the needle accommodating hole, and means for disengaging said latch from said catch upon further rotation of said drum.
 8. An attachment as recited in claim 7 wherein said last named means comprises a disk member including a flange positioned within said drum about said hub, first and second stop means radially apaced on said stop plate, abuttment means on said disk member facing said stop plate in the same radial plane as said stop means, means defining an opening in said flange, a protuberance on said latch for abutting one edge of said flange opening to rotate said disk member until said disk member abuttment means engages a first of said stop means, said stop means and abuttment means being angularly positioned such that rotation of the drum may continue subsequent to stoppage of the disk.
 9. The method of severing both the needle thread and the bobbin thread in a two thread sewing machine having a needle, and a presser foot including a needle accommodating hole, comprising the steps of: a. drawing the needle thread to a first side of said hole. b. holding said thread in this position while forming a stitch. c. pulling the needle thread further away from said hole until a predetermined amount of bobbin thread is drawn therethrough, and d. cutting both threads.
 10. The method recited in claim 9 wherein the step of drawing the needle thread comprises the step of wiping a thread engaging finger across the presser foot transverse to the direction of sewing feed to hook the thread.
 11. The method recited in claim 10 wherein said finger holds said needle thread while the needle lays a needle thread loop over said finger.
 12. The method of claim 11 wherein said step of pulling comprises lifting said finger with said thread loop thereon about a fixed axis away from said hole.
 13. The method of claim 12 wherein said step of wiping and lifting said finger comprises rotating a finger mounted wheel. 